Python Dictionaries: How to Change Key and Value

Python dictionaries are one of the most versatile data structures in the language, allowing you to store and access data in a key-value format. However, you may need to modify the keys or values of a dictionary at some point in your program. In this article, we'll discuss how to change the keys and values of Python dictionaries.

Changing the Value of a Dictionary

To change the value of a key in a Python dictionary, you can simply reassign it to a new value using the key as the index:

my_dict = {'apple': 1, 'banana': 2, 'orange': 3}
my_dict['banana'] = 4
print(my_dict)
# {'apple': 1, 'banana': 4, 'orange': 3}

In the example above, we changed the value of the 'banana' key to 4.

Changing the Key of a Dictionary

Unlike changing the value of a key, you cannot simply reassign the key to a new value. Instead, you need to create a new key-value pair with the new key and the old value, and then delete the old key-value pair. You can use the pop() method to delete the old key-value pair:

my_dict = {'apple': 1, 'banana': 2, 'orange': 3}
my_dict['pear'] = my_dict.pop('banana')
print(my_dict)
# {'apple': 1, 'pear': 2, 'orange': 3}

In the example above, we created a new key-value pair with the key 'pear' and the value of the old 'banana' key. We then deleted the old 'banana' key-value pair using the pop() method.

Combining Changing the Key and Value of a Dictionary

You can also change both the key and value of a dictionary at the same time by using a combination of the methods discussed above:

my_dict = {'apple': 1, 'banana': 2, 'orange': 3}
my_dict['pear'] = my_dict.pop('banana')
my_dict['pear'] = 4
print(my_dict)
# {'apple': 1, 'pear': 4, 'orange': 3}

In the example above, we first changed the key of the 'banana' key-value pair to 'pear', and then changed the value of the 'pear' key to 4.

Conclusion

In this article, we discussed how to change the keys and values of Python dictionaries. By using the methods discussed above, you can easily modify your dictionary to suit your needs. Python dictionaries are a powerful tool for storing and manipulating data, and understanding how to change their keys and values is an essential skill for any Python programmer.